This invention relates to an intramedullary method and apparatus for fixation of a fracture in a long bone and in particular to a method and apparatus of the type that reduces the fracture and prevents shortening of the bone segments through the use of a locked intramedullary nail.
A severely comminuted fracture in a long bone such as a tibia or femur, has a tendency to cause the bone segments created by the fracture to compress, shortening the length of the bone. Traditional treatment to prevent such compression is by skeletal traction. A known alternative is to use a cannulated intramedullary nail that is inserted into an opening made in one end of the bone and looked to the bone segments. A guide wire is first inserted in the opening, that is typically made in the proximal end of the bone, and into the distal bone fragment significantly past the fracture site. The guide wire guides the cannulated nail past the fracture site. Although the intramedullary nail substantially occupies the medullary canal, it is only capable of retaining length and preventing excessive shortening if the bone segments are appropriately fastened, or locked, to the nail.
The problem in such a locked intramedullary nail technique is locating the distal aperture(s) in the nail and successfully aligning fasteners, inserted through the bone wall, with the apertures. One known technique is the use of a jig that is accurately retained in relationship to the nail by a portion extending into the bone through the opening made in the proximal end of the bone and which has an external portion that extends parallel the bone with alignment means for aligning fasteners with the apertures in the nail provided along the external portion. While such a technique is quite successful at accurately locating the proximal locking fastener(s), the rather long distance to the distal fasteners allows relative movement between the jig and the nail which distorts the alignment means. Accordingly, alignment with the distal aperture(s) is not assured and damage to the bone wall or to the nail aperture may result.
A more accurate technique for locating the distal apertures is an X-ray imaging technique that utilizes a target device. The target device is positioned at the approximate location of the distal nail aperture and iteratively repositioned until a perfect circular image of the nail aperture is produced. This occurs when the target device is located on the centerline of the aperture. Means are provided, relative to the target device, to then locate the insertion point for the fasteners. The problem with such a distal aperture location technique is the cumulative exposure of the patient and the operating team to X-ray radiation which can be excessive if the procedure to properly position the target device results in a large number of attempts. Also, if correct alignment is not obtained, damage to the bone or nail may jeopardize the fixation.